This invention relates generally to printable identification media, namely, wristbands, labels and cards. More specifically, this invention relates to such media having a thermal sensitive coating and a protective transparent coating.
Current identification devices having thermal sensitive coatings place the thermal coating as a top layer of several layers so that the thermal coating is easily activated with thermal printheads. Some prior art devices provide a protective layer including a coating or varnish to protect the thermal layer from damage by solvents or other materials. Such varnishes are cured by ultraviolet light, can result in varying thickness following manufacture, and can result in a darker image. The darker image results because the thermal sensitive coating is not a fixed distance from the thermal print head due to the varying thickness of the varnish. This variation in distance results in a thermal sensitive coating with a greater degree of activation in areas where the over coat varnish is thinner and a lesser degree of activation in areas where the over coat varnish is thicker. Such varnishes are also soluble in certain chemicals, hand sanitizers and alcohols found in environments such as hospitals, bars, etc.
Such coatings or varnishes are problematic due to manufacturing inconsistencies such as coating thicknesses, chemical reactions with liquids that the final product may come into contact with and inconsistencies in the chemical makeup of the coating. Such issues are of greater concern to users of the products in environments where the device may come into contact with potentially damaging compounds. In one environment, healthcare facilities, the identification device may be exposed to alcohol, creams and/or gels that are harmful to the thermal or varnish layer. Another example of a harsh environment is water parks where chemicals like chlorine and exposure to harmful UV rays are present and can damage the thermal layer. The exposure to UV light and oxygen reduces the print quality and causes the print to “fade” prematurely. This is a critical problem with direct thermal printed cards, labels, tags and wristbands.
Therefore, there is a need for an identification device having a thermally activated layer that is adequately protected from harsh environments both chemical and ultraviolet. Further, there is a need for an improved coating or varnish for such thermally activated layers that will protect them from solvents or chemicals that may be used in those environments. The present invention fulfills these needs and provides other related advantages.